ADAMTS13 is a plasma metalloproteinase that regulates platelet adhesion and aggregation through cleavage of von Willebrand factor (VWF) multimers. In humans, genetic or acquired deficiency in ADAMTS13 causes thrombotic thrombocytopenic purpura (TTP), a condition characterized by thrombocytopenia and hemolytic anemia with microvascular platelet thrombi. In this study, we report characterization of mice bearing a targeted disruption of the Adamts13 gene. ADAMTS13-deficient mice were born in the expected mendelian distribution; homozygous mice were viable and fertile. Hematologic and histologic analyses failed to detect any evidence of thrombocytopenia, hemolytic anemia, or microvascular thrombosis. However, unusually large VWF multimers were observed in plasma of homozygotes. Thrombus formation on immobilized collagen under flow was significantly elevated in homozygotes in comparison with wild-type mice. Thrombocytopenia was more severely induced in homozygotes than in wild-type mice after intravenous injection of a mixture of collagen and epinephrine. Thus, a complete lack of ADAMTS13 in mice was a prothrombotic state, but it alone was not sufficient to cause TTP-like symptoms. The phenotypic differences of ADAMTS13 deficiencies between humans and mice may reflect differences in hemostatic system functioning in these species. Alternatively, factors in addition to ADAMTS13 deficiency may be necessary for development of TTP. (Blood. 2006;107:3161-3166)

Objective-Obesity is a common risk factor in insulin resistance and cardiovascular diseases. Although hypoadiponectinemia is associated with obesity-related metabolic and vascular diseases, the role of adiponectin in thrombosis remains elusive. Methods and Results-We investigated platelet thrombus formation in adiponectin knockout (APN-KO) male mice (8 to 12 weeks old) fed on a normal diet. There was no significant difference in platelet counts or coagulation parameters between wild-type (WT) and APN-KO mice. However, APN-KO mice showed an accelerated thrombus formation on carotid arterial injury with a He-Ne laser (total thrombus volume: 13.36Ϯ4.25ϫ10 7 arbitrary units for APN-KO and 6.74Ϯ2.87ϫ10 7 arbitrary units for WT; nϭ10; PϽ0.01). Adenovirus-mediated supplementation of adiponectin attenuated the enhanced thrombus formation. In vitro thrombus formation on a type I collagen at a shear rate of 250 s Ϫ1 , as well as platelet aggregation induced by low concentrations of agonists, was enhanced in APN-KO mice, and recombinant adiponectin inhibited the enhanced platelet aggregation. In WT mice, adenovirus-mediated overexpression of adiponectin additionally attenuated thrombus formation. Key Words: acute coronary syndromes Ⅲ obesity Ⅲ platelets Ⅲ thrombosis O besity is associated with insulin resistance, accelerated atherothrombosis, and cardiovascular diseases. 1,2 Recent studies have revealed that adipose tissue is not only a passive reservoir for energy storage but also produces and secretes a variety of bioactive molecules, known as adipocytokines, including tumor necrosis factor (TNF) ␣, leptin, resistin, and plasminogen activator inhibitor type-1. [2][3][4] Dysregulated production of adipocytokines participates in the development of obesityrelated metabolic and vascular diseases. [2][3][4] Adiponectin is an adipocytokine identified in the human adipose tissue cDNA library, and Acrp30/AdipoQ is the mouse counterpart of adiponectin (reviewed in reference 5 ). Adiponectin, of which mRNA is exclusively expressed in adipose tissue, is a protein of 244 amino acids consisting of 2 structurally distinct domains, an N-terminal collagen-like domain and a C-terminal complement C1q-like globular domain. Adiponectin is abundantly present in plasma (5 to 30 g/mL), and its plasma concentration is inversely related to the body mass index. 5 Plasma adiponectin levels decrease in obesity, type 2 diabetes, and patients with coronary artery disease (CAD). 5-9 Indeed, adiponectin (APN) knockout (KO) mice showed severe diet-induced insulin resistance. 10 In cultured cells, we have demonstrated that human recombinant adiponectin inhibited the expression of adhesion molecules on endothelial cells, the transformation of macrophages to foam cells, and TNF-␣ production from macrophages. 5,11 Furthermore, APN-KO mice showed severe neointimal thickening in mechanically injured arteries. 12 Adenovirusmediated supplementation of adiponectin attenuated the development of atherosclerosis in apolipoprotein E-deficient mice as well as postinj...

Background-The short-term clinical benefits of bone marrow mononuclear cell transplantation have been shown in patients with critical limb ischemia. The purpose of this study was to assess the long-term safety and efficacy of bone marrow mononuclear cell transplantation in patients with thromboangiitis obliterans. Methods and Results-Eleven limbs (3 with rest pain and 8 with an ischemic ulcer) of 8 patients were treated by bone marrow mononuclear cell transplantation. The patients were followed up for clinical events for a mean of 684Ϯ549 days (range 103 to 1466 days). At 4 weeks, improvement in pain was observed in all 11 limbs, with complete relief in 4 (36%). Pain scale (visual analog scale) score decreased from 5.1Ϯ0.7 to 1.5Ϯ1.3. An improvement in skin ulcers was observed in all 8 limbs with an ischemic ulcer, with complete healing in 7 (88%). During the follow-up, however, clinical events occurred in 4 of the 8 patients. The first patient suffered sudden death at 20 months after transplantation at 30 years of age. The second patient with an incomplete healing of a skin ulcer showed worsening of the lesion at 4 months. The third patient showed worsening of rest pain at 8 months. The last patient developed an arteriovenous shunt in the foot at 7 months, which spontaneously regressed by 1 year. Conclusions-In the present unblinded and uncontrolled pilot study, long-term adverse events, including death and unfavorable angiogenesis, were observed in half of the patients receiving bone marrow mononuclear cell transplantation. Given the current incomplete knowledge of the safety and efficacy of this strategy, careful long-term monitoring is required for future patients receiving this treatment.

ADAMTS13 is a multidomain protease that limits platelet thrombogenesis through the cleavage of von Willebrand factor (VWF). We previously identified 2 types of mouse Adamts13 gene: the 129/Sv-strain Adamts13 gene encodes the long-form ADAMTS13 having the same domains as human ADAMTS13, whereas the C57BL/6-strain Adamts13 gene encodes the short-form ADAMTS13 lacking the distal C-terminal domains. To assess the physiologic significance of the distal C-terminal domains of ADAMTS13, we generated and analyzed 129/Sv-genetic background congenic mice (Adamts13 S/S ) that carry the short-form ADAMTS13. Similar to wild-type 129/Sv mice (Adamts13 L/L ), Adamts13 S/S did not have ultralarge VWF multimers in plasma, in contrast to 129/Svgenetic background ADAMTS13-deficient mice (Adamts13 ؊/؊ ). However, in vitro thrombogenesis under flow at a shear rate of 5000 s ؊1 was accelerated in Adamts13 S/S compared with Adamts13 L/L . Both in vivo thrombus formation in ferric chlorideinjured arterioles and thrombocytopenia induced by collagen plus epinephrine challenge were more dramatic in Adamts13 S/S than in Adamts13 L/L but less than in IntroductionADAMTS13 is a plasma protease that specifically cleaves von Willebrand factor (VWF). 1 VWF is a multimeric plasma glycoprotein that plays a critical role in platelet adhesion and aggregation on vascular lesions. 2 Endothelial cells and megakaryocytes produce mainly VWF as large multimers that can exceed 20 000 kDa in mass and secrete the multimers into the circulating blood. The adhesive activity of VWF multimers depends on their molecular sizes and in particular the largest multimers, called ultralarge VWF (UL-VWF) multimers, can induce excessive platelet aggregation under shear stress. UL-VWF multimers are normally cleaved by ADAMTS13 to smaller forms, thus restraining platelet thrombus formation. The lack of ADAMTS13 activity allows UL-VWF multimers to persist in the circulation and leads to the development of thrombotic thrombocytopenic purpura (TTP). [3][4][5] ADAMTS13 consists of multiple domains including a metalloprotease domain, a disintegrin-like domain, a thrombospondin type 1 motif (Tsp1) domain, a cysteine-rich domain, a spacer domain, 7 additional Tsp1 domains and 2 complement components C1r/ C1s, urchin epidermal growth factor, and bone morphogenic protein-1 (CUB) domains in order from the N-terminus. So far, the functional roles of ADAMTS13 domains have been studied using in vitro assay systems. [6][7][8][9][10][11][12][13] These studies have shown an essential role of the N-terminal region of ADAMTS13 from the metalloprotease domain to the spacer domain, on the VWF cleavage. However, the results from in vitro studies have lacked consistency on the relative importance of the C-terminal Tsp1 and CUB domains in the substrate recognition and the activity of ADAMTS13. The recombinant human ADAMTS13 mutant lacking the C-terminal Tsp1 and CUB domains maintain almost absolute VWF-cleaving activity under static conditions, indicating that the C-terminal domains are dispensab...